Developing device for electrostatic latent image

ABSTRACT

An apparatus for developing an electrostatic latent image which comprises a plurality of developing units in series for conveying electrophotographic material smoothly therethrough, each unit comprising (a) a downwardly inclined endless belt provided with protruding ridges along the sides of a surface thereof for conveying electrophotographic sheet material and further provided with an electroconductive layer and (b) a driving mechanism for the endless belt, a plurality of liquid developer feeding nozzles and side plates respectively associated with the developing units disposed at points lower than the path of the electrophotographic sheet material and further disposed, for each developing unit, at the proximity of the uppermost portion of the endless belt, and means contacting the endless belt under the feeding nozzles for cleaning the endless belt thereby holding the liquid developer in a concave part formed by the endless belt, side plates, developer feeding nozzles and the cleaning means, the endless belt feeding the liquid developer thus held in the concave part to the electrophotographic sheet material.

United States Patent 1 [191 Sato et a1.

[ DEVELOPING DEVICE FOR ELECTROSTATIC LATENT IMAGE [75] Inventors: Masamichi Sato; Osamu Fukushima,

both of Asaka, Japan [73] Assignee: Fuji Photo Film Co., Ltd., Minami vAs ewi,. =r s Japan 22 Filed: Jan. 8, 1971 21 Appl. No.: 105,052

g [30] Foreign Application Priority Data Jan. 8, 1971 Japan 46/2588 [52] U.S. Cl 1.18/637, 117/37 LlE, 118/D1G. 23, 355/10 [51] Int. Cl. G03g 13/00 [58] Field of Search 118/637, DIG. 23, 118/259, 324, 407; 117/37 LE, 93.4 R,

[56] References Cited UNlTED STATES PATENTS 3,308,737 3/1967 Susumu Fukuda 95/89 R 2,442,876 6/1948 Pearson 118/407 3,369,523 2/1968 Naumann, 118/637 3,669,073 6/1972 Sauit et a1 118/637 3,566,834 3/1971 Tamai et a1....-. 118/637 3,643,628 2/1972 Sugarman et a1. 118/637 3,601,092 8/1971 Satomi 118/637 OTHER PUBLICATIONS R. W. Keyes, Liquid Crystal Electrophotographic Get. 23, 1973 Display, lBM Tech. Disclosure, Vol. 12, No. 12 May 1970.

Primary Examiner-Mervin Stein Assistant Examiner-Leo Millstein Att0rneyAddams & Ferguson [5 7] ABSTRACT An apparatus for developing an electrostatic latent image which comprises a plurality of developing units in series for conveying electrophotographic material smoothly therethrough, each unit comprising (a) a downwardly inclined endless belt provided with protruding ridges along the sides of a surface thereof for conveying electrophotographic sheet material and further provided with an electroconductive layer and (b) a driving mechanism for the endless belt, a plurality of liquid developer feeding nozzles and side plates respectively associated with the developing units disposed at points lower than the path of the electrophotographic sheet material and further disposed, for each developing unit, at the proximity of the uppermost portion of the endless belt, and means contacting the endless belt under the feeding nozzles for cleaning the endless belt thereby holding the liquid developer in a concave part formed by the endless belt, side plates, developer feeding nozzles and the cleaning means, the endless belt feeding the liquid developer thus held in the concave part to the electrophotographic sheet material.

2 Claims, 5 Drawing Figures PATENIEDomaaasrs 3.766387 SHEET 10F 2 FIG.2

- 1 DEVELOPING DEVICE FOR ELECTROSTATIC LATENT IMAGE V This invention relates to an apparatus for liquid development of electrostatic latent image formed on an electrophotographic material, and particularly to a developing apparatus capable of providing satisfactory image quality without showing streaks? on the image even developed at a higher speed.

BRIEF DESCRIPTION OF DRAWING FIGS. 1 and 2 are schematic cross-sectional side views of the conventional developing apparatus for electrostatic latent image. 7

FIG. 3 is a schematic side view of an example ofdeveloping apparatus-embodying this invention.

FIGS. 4 and 5 are perspective view of principal portion and cross sectional side view, respectively, of the apparatus of FIG. 3.

In the prior apparatus for liquid development of electrostatic latent image, the means of supplying liquid developer can be represented as in FIG. 1 or FIG. 2 according to its principle. The apparatus of FIG. 1 in which liquid developer 14 is introducedbetween the surface 11 holding latent image and the developing electrode 12 essentially involves adrawback in resulting streaks on the image due to the presence of relative speed between the surface 11 and the liquid developer. Said streaks becomemore marked when the distance between the surface holding the latent image and the developing electrode is small, and therefore the developing apparatus of this type is not suitable for obtaining continuous tone image of high quality ata high speed. v

FIG. 2 shows an example of developing apparatus whichis designed so as not to form relative speed between the surfaceholding the latentimage and the liquid developer, in order to suppress the phenomenon of streaks.

In" FIG. 2a metal. drum 21 is rotated in the direction of arrow 23, and thelower part of said drum is immersedinto the liquid developer 25 contained in a container-24. Thus the drum 21 -is brought into contact with theliquiddeveloper at the lower part thereof and forms thin layer of said liquid developer onfthe surface thereof, andbrings the thin layer th'usformed upwards. On the other hand the sheet 11 with the latent image formed thereon is advanced above said drum 21 in the direction of arrow 22 and is brought into contact with.

alongthe surface of said drum by means of gravity when this is brought up by adhesion to said Consequently the amount of toner coming into contact with the surface holding the latent image becomes insufficient, and thus it is impossible to obtain desirable developing density even if the developing speed is made very small.

The present invention is to provide a developing apparatus capable of realizing development at a high speed without employing the developing liquid of high concentration and high viscosity, and furthermore without showing streaks on the image obtained.

FIG. 3 shows the schematic cross-sectional sideview of an apparatus embodying the present invention adapted for processing electrophotographic sheet material carrying electrostatic latent image thereon. In this apparatus theelectrophotographic material 101 (hereinafter expressed as the sheet) is supplied into the apparatus by means of a pair of pinch rollers 102 and 103 with the image-holding surface down. Said pinch roller 103 is composed of sponge or insulating rubber in order to apply insulating prebath solution to said image-holding surface. Said prebath solution prevents the formation of fogging on the electrophotographic image to be obtained. The sheet 101 treated with prebath solution is subjected to development on an endless belt 106 driven in the same direction with cm, respectively. The liquid developer is supplied from the holes provided on the wall of pipe 205 to the gap between the sheet 101 and the endless belt 106, and the development of latent image carried on the sheet 101 is carried out using said endless belt 106 as the developing electrode. The streak on the image obtained is prespeed between the surface holding the latent image and the liquid developer is made very small and the streaks of the image is prevented if the peripheral speed of drum 21' is substantially equal tothe advancing speed of said sheet 11. In the developing apparatus of FIG. 2,

however, it is difficult to obtain sufficiently high developed density since the contact time between the surface holding the latent image and the liquid developer is very short. lt-is actually possible to obtain considerably satisfactory. image by employing a-liquid developer of high tonerconcentration and high viscosity if low develop'ing speed is permissible. Such developer of high concentration and high viscosity will result in, however, the higher stain ,level due to developer and inevitably cause the problem of preventing fogging resulting therefrom. On the other hand the liquid developer of lower concentration and lower viscosity will flow down vented since the sheet 101, developing liquid and the endless belt 106 advance at a same speed. A roller 209 is provided in order to maintain the distance between the sheet 101 and theendless belt 106 sandwiching the liquid developer therebetween and is driven by the movement of the sheet 101. The upper surface of said endless belt l06 is inclined a little, as shown in the drawing, in order to facilitate the supply of liquid developer. The toner image formed remains intact since the endless belt 106 and the sheet 101 are maintained at a same speed and because of the presence of said liquid Further provided are plural sets, preferably 4 Q 10 sets of similar developing unit involving the endless belts 110, 111, 112, which are driven at a same speed. The last endless belt 112 is inclined in the opposite direction with respect to others in order to prevent the flowing of liquid developer into the succeeding processing stage. The use of plural endless belts intends to prolongate the developing time in order to obtain sufficient developing density and to compensate the unevenness in the developing resulting from uneven supply of liquid developer.

FIGS. 4 and 5 are the perspective view of the principal part and cross sectional side view, respectively,

showing an example of the mechanism supplying liquid the side wall thereof in order to feed the liquid developer between the endless belt 206 andthesheet 101.

The mechanism is further provided with a side plate 202 supporting said pipe 205 at the extremities thereof .and preventing the leakage of liquid developer from the sides of said endless belts, a rigid curved plate 203 provided underv said pipe 205 and along the surface of said endless belt 206 'beng along the'surface of .the roller 107, and felt or sponge 204 attached to the lower surface of said rigid curved plate 204 and coming into contactl'with the surface of said endless belt 206. The endless belt 206 is further provided with protruding ridges 201 at the sides thereof in order to prevent the leakage of liquid developer therefrom. Flanged rollers 207. of which movement in the direction of sheet advancement is limited for example by suitable vertical recess are placed on the sheet 101 and are rotated by the friction with said sheet 101. The distance between the outer surfaces of the flanges of said roller 207 is made a little smaller than the distance between the protruding ridges provided on thesides of endless belts, and the width of the sheet 101 to be employed in this apparatus'is a little less belt and the sheet are to be separated.

The sheet thus processed is reversed by curved lattice type guide 113, and placed on 'a chain or metal mesh endless belt driven by the rollers 115 and Y116. Cleaning liquid sprayed from the nozzles 117, 118 and 119 cleans the both surfaces of the sheet 101 thus far provided with the pipe 205 by means of a pump (not a container 130 from the lowest end of the endless belt 106. The liquid developer still remaining on said endless belt 106 is scraped off by the flannel or sponge 204 provided on the rigid curved plate 203. The liquid developer collected in the container 130 is cycled again to the pipe 205 by a pump. I

The sheet 101 having sufficient stiffness is automatically transferred to thesucceeding endless belt at the junctions of endless belts. If the sheet cannot have the sufficient stiffness for this purpose, it is recommended to provide a sep arating claw at'the part where the endcessed to remove excessive toner thereby preventing fogging and stain. The cleaning liquid after use is recovered in the container 140. Also provided is a pair of squeeze rollers 116 and 120.

As thus far explained, the apparatus of this invention prevents the formation of streaks" on the. image obtained since the sheet and the endless belt are advanced at a same speed, and enables to obtain the image of elevated optical density without employing liquid developer of high toner concentration since sufficient amount of developer can be supplied to the surface holding the latent image. This fact simultaneously prevents the formation of fogging or stain. Thus it is made possible to obtain the image of high quality by means of the apparatus of this invention.

We claim:

1. An apparatus for developing an electrostatic latent.

image which comprises a plurality of developing units inseries for conveying electrophotographic material smoothly therethrough, each said unit comprisingla) a downwardly inclined endless belt provided with protruding ridges along the sides of a surface thereof for conveying electrophotographic sheet material and further provided with an electroconductive layer and (b) a driving mechanism for said endless belt, a plurality of liquid developer feeding nozzles and side plates respectively associated with said developing units disposed at points lower than the path of said electrophotographic sheet material and further disposed, for each developing unit, at the proximity of the uppermost portion of said endless belt, and means contacting said endless belt under said feeding nozzles for cleaning said endless belt thereby holding the liquid developer in a concave part formed by the endless belt, side plates, developer feeding nozzles and said cleaning means, said endless belt feeding the liquid developer thus held in the con-.

cave part to the electrophotographic sheet material.

2. Apparatus as in claim'l where theendless beltfof the last of said developing units is inclined in the opposite direction with respect to the remainder of said belts to inhibit the flow of liquid developer from said last developing unit. 

1. An apparatus for developing an electrostatic latent image which comprises a plurality of developing units in series for conveying electrophotographic material smoothly therethrough, each said unit comprising (a) a downwardly inclined endless belt provided with protruding ridges along the sides of a surface thereof for conveying electrophotographic sheet material and further provided with an electroconductive layer and (b) a driving mechanism for said endless belt, a plurality of liquid developer feeding nozzles and side plates respectively associated with said developing units disposed at points lower than the path of said electrophotographic sheet material and further disposed, for each developing unit, at the proximity of the uppermost portion of said endless belt, and means contacting said endless belt under said feeding nozzles for cleaning said endless belt thereby holding the liquid developer in a concave part formed by the endless belt, side plates, developer feeding nozzles and said cleaning means, said endless belt feeding the liquid developer thus held in the concave part to the electrophotographic sheet material.
 2. Apparatus as in claim 1 where the endless belt of the last of said developing units is inclined in the opposite direction with respect to the remainder of said belts to inhibit the flow of liquid developer from said last developing unit. 